Taking A Multi-Input Approach to Emergency Caller Location

About the Author

Adrian Stimpson

Adrian is the Senior Vice-President of Sales and Marketing at Rx Networks.

You witness a serious car crash. What’s the first thing you do? You instinctively grab your phone and dial 911. One of the most important contributions of technology has been, and will continue to be, its ability to save lives. While this may mean the impressive equipment available in a modern hospital emergency room, first someone has to call for an ambulance to get you there.

The history of the one-number emergency calling system provides an interesting perspective on how long it can take to deploy new technology in a way that is integrated and reliable. It is a long road from demonstration to widespread public adoption.

The history of one number emergency calling goes back about 90 years. As public switched telephone networks spanned the modern world in the middle of the 20th century, it became apparent that they could play a vital role in reaching providers of emergency services. The concept of a short form single number was developed as “999” in the UK and first deployed in 1937. I can only imagine the frustration on a rotary phone as you waited for the dial to rotate almost the maximum possible time to send three digits (this was due to the fact that phones could make free calls using the neigbouring “0” digit, so mechanically modifying them to accept any sequence of 9’s, the next digit, was easier than implementing “111”).

The first uses of a central emergency service in North America include Los Angeles in 1946 (using “116”), Winnipeg in 1959 (using “999”), and the first system using “911” in Haleyville, Alabama in 1968. Gradually, through the 1970’s and 1980’s the deployment of what is now “911” service reached all but the most rural areas. Approximately 50 years to standardize and implement!

Extension of the emergency service to mobile phones was first contemplated with the roll out of analog cellular networks in the mid 1980’s. It quickly became apparent that mobile phones could play a key role in getting first responders to car accidents and other emergencies outside the home. But once away from home, people are often have trouble describing where they are, either because of unfamiliar surroundings or the shock of the situation in progress. An automatic method of location determination needed to be found.

In the 1990’s, it was foreseen that the steadily decreasing price of GPS chips and the increasing “smarts” available within network infrastructure would eventually enable reliable location of emergency callers in 2D (lat/lon). In 1996, the FCC formalized this, mandating requirements for mobile operators to provide location using GPS within 50 meters for 67% of calls and 150 meters for 90% of calls or to provide location using network based technology within 100 meters and 300 meters, 67% and 90% of the time respectively.

So now, when you dial 911, the Public Safety Answering Point (PSAP) is able to accurately determine your location… for the most part. That is, if you are outside or in a low-rise, residential type building.

However, what will happen if you dial 911 from the 32nd floor of an office tower? First of all, you may not get a GPS fix or sufficiently accurate network fix – there are significant attenuation and multipath issues to contend with. If you do get a fix, the PSAP will match your latitude/longitude to a database that will give your location as, for example, 250 Greenwhich Street, Manhattan. But that is a 52-story building! By the time the search for you gets to the 32nd floor it might be too late.

In March, 2014, in an effort to address this, the FCC issued a “Notice of Proposed Rulemaking” to seek comment on a proposed mandate that would require mobile operators to more accurately determine the location of an indoor 911 call. There were many questions posed about whether the requirements should be different for urban vs. rural locations, whether today’s technology can meet the requirements, whether certain technology should be mandated or simply an accuracy requirement be asserted, and much more.

Responses were received from a variety of stakeholders, with thoughtful and passionate responses from network operators, emergency services providers, the public, and technology vendors.

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